This disclosure relates to evaluating cement behind a casing of a wellbore and, or particularly, to cement evaluation data processing associated with a solid-liquid-gas (SLG) model map.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light.
A wellbore drilled into a geological formation may be targeted to produce oil and/or gas from certain zones of the geological formation. To prevent zones from interacting with one another via the wellbore and to prevent fluids from undesired zones entering the wellbore, the wellbore may be completed by placing a cylindrical casing into the wellbore and cementing the annulus between the casing and the wall of the wellbore. During cementing, cement may be injected into the annulus formed between the cylindrical casing and the geological formation. When the cement properly sets, fluids from one zone of the geological formation may not be able to pass through the wellbore to interact with one another. This desirable condition is referred to as “zonal isolation.” Yet well completions may not go as planned. For example, the cement may not set as planned and/or the quality of the cement may be less than expected. In other cases, the cement may unexpectedly fail to set above a certain depth due to natural fissures in the formation.
A variety of acoustic tools may be used to verify that cement is properly installed. These acoustic tools may use pulsed acoustic waves as they are lowered through the wellbore to obtain acoustic cement evaluation data (e.g., flexural attenuation and/or acoustic impedance measurements). A solid-liquid-gas (SLG) model map may be used to interpret the acoustic cement evaluation data to indicate whether solids, liquids, or gases are in the annulus behind the casing of the wellbore. When the SLG model map indicates that a solid is present, the cement is likely to have set properly. When the SLG model map indicates that a liquid or gas is present, the cement may be interpreted not to have properly set or otherwise may not be seen. Although the SLG model map can be used to map acoustic measurements to a probabilistic state of the material behind the casing (e.g., solid, liquid, or gas), certain well logging conditions, such as light cement, can challenge the effectiveness of the SLG model map.